Protective coating composition

ABSTRACT

A radiation polymerizable protective coating composition or paint, coated articles bearing such a protective coating and processes for preparing such articles. The radiation polymerizable paint, on a non-polymerizable solvent, pigment, initiator and particulate filler-free basis consists essentially of a binder solution of: (1) an alpha-beta olefinically unsaturated organic resin containing between about .5 and about 5 units of olefinic unsaturation per 1,000 units of molecular weight; (2) a compound polymerizable with said resin upon exposure to ionizing radiation; and (3) between about 1.0 and about 15.0 parts per 100 parts of the total of said alpha-beta olefinically unsaturated resin and said compound polymerizable therewith of a triester of phosphoric acid bearing one or more sites of vinyl unsaturation. The composition exhibits excellent quality and good adhesion to a variety of substrates, in particular metals, including vapor deposited metals. Preferred articles bearing such a coating are prepared by: applying a base coat to a substrate and curing the same; vapor depositing a coating of a metal over the surface of the base coat; and applying to and curing on the surface of the deposited metal the radiation polymerizable topcoat, preferably with little or no pigment contained therein.

This application relates to: radiation polymerizable coatings ofexcellent quality which display unusually good adhesion to a variety ofsubstrates; coated articles bearing such a radiation polymerizablecoating; and processes for preparing such articles.

More particularly, this application relates to radiation polymerizablecoating compositions which are particularly suited as corrosion andabrasion resistant protective coatings for vapor deposited metalsurfaces as well as to articles comprising such a vapor deposited metalsurface bearing the protective coating and processes for preparing thesame. Such protectively coated, vapor deposited metal bearing articlesare a particularly preferred embodiment of the invention since they aresuitable for use as a substitute for plated metal surfaces used for trimor brightwork on the exterior of automobiles.

Still more particularly, this application relates to an improvement ofcoating compositions which generally, exclusive of nonpolymerizablesolvents, pigments and other non-reactive components, consistessentially of a film forming solution of: (1) an alpha-betaolefinically unsaturated organic resin containing between about 0.5 andabout 5 units of olefinic unsaturation per 1,000 units of molecularweight; and (2) a compound polymerizable therewith upon exposure toionizing radiation. Representative of such radiation polymerizablecoating compositions are those disclosed in the following U.S. Pat.Nos.: 3,437,514; 3,437,512; 3,437,513; 3,528,844; 3,542,586; 3,542,587;3,577,262; 3,577,263; 3,577,264; 3,577,265; 3,585,065; 3,586,528;3,586,530; 3,632,399; 3,641,210; 3,642,939; 3,649,337; 3,650,811;3,650,812; 3,650,813; 3,660,143; 3,660,144; 3,660,145; and 3,660,471;Although the compositions disclosed in each of these patents will bediscussed further hereinafter, the complete disclosure of each of thepatents is incorporated herein by reference.

The coatings disclosed by the above patents may be classified as finishcoatings and, as such, are required to provide not only an excellentappearance, but also physical properties which will enable the coatedpart to withstand the elements to which it may be exposed. Although thecoatings are suitable to provide an external finish on a variety ofsubstrates, they do not adhere well to metal or metal bearing substratessuch as those having vapor deposited metal surfaces nor do they provideadequate corrosion protection when applied to such surfaces. The coatingcompositions of this invention solve such problems by providing improvedcorrosion resistance and adhesion, particularly when applied to surfacebearing vapor deposited metal coatings.

BRIEF DESCRIPTION OF THE INVENTION

The coating compositions of this invention, on a non-polymerizablesolvent pigment, initiator and particulate filler-free basis consistessentially of a binder solution of: (1) an alpha-beta olefinicallyunsaturated organic resin containing between about 0.5 and about 5 unitsof olefinic unsaturation per 1,000 units of molecular weight; (2) acompound polymerizable with said resin upon exposure to ionizingradiation; and (3) between about 1.0 and about 15.0 parts per 100 partsof the total of said alpha-beta olefinically unsaturated resin and saidcompound polymerizable therewith of a triester of phosphoric acidbearing one or more sites of vinyl unsaturation and having the formula:##STR1## where: R = H, C1 or CH₃

A = cnH_(2n), 2 ≦ n ≦ 6

R' = c₁ to C₄ alkyl or C₁ to C₄ chloro- or bromo-alkyl

These coating compositions, which are radiation polymerizable, arepreferably cured by exposure to ionizing radiation or ultravioletradiation. The coating compositions provide an excellent protectivesurface which adheres well to a variety of substrates, in particularmetals and vapor deposited metals, and, thus, can be employed in thepreparation of a wide variety of articles. One such preferred article ormaterial, which is useful as a substitute for metal plated materialsused for trim or brightwork on the exterior of automobiles, is preparedby: (1) vapor depositing a metal layer on the surface of a preparedsubstrate; (2) coating the deposited metal surface with the radiationpolymerizable coating of this invention; and (3) curing the coating byexposure to radiation, preferably ionizing radiation or ultravioletradiation.

The radiation polymerizable coating composition and the coated articlesformed therefrom as well as the processes for preparing the same will bedescribed more fully in the detailed description of the invention whichfollows.

DETAILED DESCRIPTION OF THE INVENTION I. Radiation Polymerizable CoatingComposition

In this application, the term "paint" is meant to include finely dividedpigment and/or particulate filler as well as other additives in afilm-forming, resin comprising, binder or the binder without pigment,particulate filler, and other additives. Thus, the binder which isultimately converted to a weather and wear-resistant film can be all orvirtually all that is used to form the film, or it can be a vehicle forpigment and other additives.

The radiation polymerizable coating compositions or paints of thisinvention, which overcome the deficiencies of prior art coatings, on anon-polymerizable solvent, pigment, initiator and particulatefiller-free basis, consist essentially of a binder solution of: (1) analpha-beta olefinically unsaturated organic resin containing betweenabout .5 and about 5 units of olefinic unsaturation per 1,000 units ofmolecular weight; (2) a compound polymerizable with said resin uponexposure to ionizing radiation; and (3) between about 1.0 and about 15.0parts per 100 parts of the total of said alpha-beta olefinicallyunsaturated resin and said compound polymerizable therewith of atriester of phosphoric acid bearing one or more sites of vinylunsaturation and having the formula: ##STR2## where: R = H, C1 or CH₃

A = c_(n) H_(2n), 2 ≦ n ≦ 6

R' = c₁ - c₄ alkyl or

C₁ - c₄ bromo- or chloroalkyl

A. ALPHA-BETA OLEFINICALLY UNSATURATED RESINS

The term "alpha-beta olefinically unsaturated organic resin" as usedherein means an organic resin having olefinic unsaturation provided byan alpha-beta olefinically unsaturated monomer. The term "alpha-betaunsaturation" as used herein includes both the olefinic unsaturationthat is between two carbon atoms which are in the alpha and betapositions relative to an activating group such as a carboxyl group,e.g., the olefinic unsaturation of maleic anhydride, and the olefinicunsaturation between the two carbon atoms which are in the alpha andbeta positions with respect to the terminus of an aliphaticcarbon-to-carbon chain, e.g., the olefinic unsaturation of acrylic ormethacrylic acid or styrene. The binder solution of the coatingcompositions of this invention preferably includes between about 90 andabout 10 parts, preferably between about 80 and about 20 parts of suchan alpha-beta olefinically unsaturated resin containing between about0.5 and about 5 units, preferably between about 0.5 and about 3 units,of unsaturation per 1,000 units of molecular weight. The selection ofthe particular alpha-beta olefinically unsaturated organic resin will,of course, depend upon the particular selection of the compoundpolymerizable therewith as well as the type of substrate being coated,the intended use of the end product and the desired viscosity of thebinder, keeping in mind the desired mode of application. The followingdiscussion of alpha-beta olefinically unsaturated resins is presented asa summary of the various types of resins which may be employed inradiation curable paints known in the prior art and taught in theabove-incorporated prior art patents. Of course, the particular detailsregarding the various prior art radiation curable compositions are moreadequately described in the patent disclosures incorporated herein byreference.

U.S. Pat. No. 3,437,514 to Burlant discloses a number of preferred typesof alpha-beta olefinically unsaturated resins useful in this invention,which types are generic to a number of resins disclosed by others of thepatents listed above. One of these resins is of the vinyl resin type.The term "vinyl resin" as used in this context is one which is formedfrom "vinyl monomers" and which includes the requisite amount ofalpha-beta olefinic unsaturation. The term "vinyl monomers" is intendedto mean monomeric compounds having a ##STR3## terminal group andexcludes allylic compounds, resins and modified acrylic resins, theformer meaning a resin formed exclusively of acrylic monomers and thelatter meaning a resin formed from a major amount of acrylic monomersand a minor amount of non-acrylic monomers. The term "acrylic monomers"means an alpha-beta monounsaturated monocarboxylic acid or estersthereof and includes, but not by way of limitation, acrylic acid,alkylacrylic acids, e.g., methacrylic acids, monohydric and polyhydricalcohol esters of acrylic acid and alkylacrylic acids, e.g., glycidylmethacrylate, 2-hydroxethyl methacrylate, etc. These resins have amolecular weight in excess of about 1,000, commonly about 5,000 to about25,000. Similar alpha-beta olefinically unsaturated vinyl monomercontaining polymers are disclosed in U.S. Pat. Nos. 3,528,844;3,542,586; 3,542,587; 3,577,265; 3,586,529; 3,586,528; 3,586,530;3,641,210; and 3,642,939. All of these vinyl monomer containing polymersmay be prepared by conventional free radical initiated copolymerizationusing two or more, preferably three or more, vinyl monomers at least oneof which has a free or pendant functional group within its molecularstructure, e.g., hydroxyethyl methacrylate. This functionality allowsthe polymer intermediate to then be reacted with various other monomerssuch as glycidyl methacrylate to provide the desired alpha-beta olefinicunsaturation.

A second type of alpha-beta olefinically unsaturated organic resindisclosed by U.S. Pat. No. 3,437,514 is a polyester having a molecularweight greater than 1,000 and preferably between about 2,000 and about20,000. The preferred polyester is a copolymerization product of apolyhydric alcohol, and an acyclic, alpha-unsaturated alpha-betadicarboxylic acid, and a cyclic aliphatic dicarboxylic acid. U.S. Pat.No. 3,577,262 also discloses such an alpha-beta olefinically unsaturatedpolyester. U.S. Pat. Nos. 3,649,337 and 3,660,371 disclose relatedunsaturated polyester resins formed by reacting an alpha-betaolefinically unsaturated, monocarboxy terminated, polyester with anepoxy functional graded-rubber particle.

A third type of unsaturated organic resin useful in this invention andtaught by the Burlant patent is a silicone-modified organic resincomprising a polyester having incorporated therein a cyclic or acyclicsiloxane which prior to reaction of incorporation has a reactivehydroxyl or hydrocarbonoxy group bonded to at least two of its siliconatoms. Such a resin can also be prepared by reacting a siloxane with ahydroxylated vinyl resin prepared by reacting vinyl monomers, at leastone of which is a hydroxylated monomer. Various modifications of resinsof this type are taught in U.S. Pat. Nos. 3,437,512; 3,437,513;3,650,811; 3,650,812; 3,650,813; 3,577,264 and 3,632,399.

A fourth alpha-beta olefinically unsaturated organic resin disclosed byBurlant and useful in this invention is a urethane-modified organicpolymer formed by reacting a diisocyanate monomer and an organic resinhaving in its molecular structure a plurality of hydrogen atoms whichare labile with respect to an isocyanate group.

A final category of alpha-beta olefinically unsaturated organic resinsdisclosed by Burlant comprises epoxy resins having requisite amounts ofunsaturation. Similar epoxy containing resins are also disclosed in U.S.Pat. Nos. 3,577,263 and 3,660,145.

Still other alpha-beta olefinically unsaturated resins are taught byseveral of the patents enumerated above. For example, both U.S. Pat.Nos. 3,660,144 and 3,660,145 teach alpha-beta olefinically unsaturatedelastomeric particles of cross-linked acrylic polymer for use inradiation curable paints and U.S. Pat. No. 3,585,065 teaches analpha-beta olefinically unsaturated siloxane resin for use in afilm-forming binder system. Of course, the subject invention is notlimited to the types of unsaturated resin summarized above, but mayinclude any alpha-beta olefinically unsaturated organic resin having therequisite unsaturation and being polymerizable upon being subjected toionizing radiation. It should also be appreciated that the radiationpolymerizable paints of this inventon may also employ mixtures of thevarious alpha-beta olefinically unsaturated organic resins where desiredfor the particular application.

B. COMPOUND POLYMERIZABLE WITH ALPHA-BETA OLEFINICALLY UNSATURATED RESIN

The compound polymerizable by exposure to ionizing radiation with thealpha-beta olefinically unsaturated organic resin is included in thepaint binder solution in an amount ranging between about 90 and about 10parts, preferably between about 80 and about 20 parts. The compound ispreferably a vinyl monomer as defined above or a mixture of vinylmonomers. The preferred vinyl monomers taught by the above patents areesters of C₁ - C₈ monohydric alcohols and acrylic or methacrylic acids,e.g., methylmethacrylate, ethyl acrylate, butyl acrylate, butylmethacrylate, octyl acrylate, 2-ethyl hexylacrylate, etc. Alcohols ofhigher carbon numbers, e.g., C₉ - C₁₅ as well as difunctional alcoholscan also be used to prepare esters or diesters. Vinyl hydrocarbonmonomers, e.g., styrene and alkylated styrenes such as vinyl toluene,alphamethyl styrene, etc., may also be used separately or in combinationwith the aforementioned vinyl monomers. In combination with the acrylatemonomers and/or vinyl hydrocarbon monomers, there may be used minoramounts of other vinyl monomers such as nitriles, e.g., acrylonitrile,acrylamide or n-methylol carboxylates, e.g., vinyl acetate. Such vinylmonomers are useful in combination with each of the alpha-betaolefinically unsaturated resins discussed previously and taught by thevarious patents.

Other vinyl containing compounds which may be employed in combinationwith the alpha-beta olefinically unsaturated resins are divinylmonomers, trivinyl monomers, tetravinyl monomers and mixtures thereof.These di-, tri-, and tetravinyl compounds are preferably acrylates,methacrylates or vinyl hydrocarbons. The most preferred are esters ofacrylic or methacrylic acids and polyhydric C₂ - C₈ alcohols, e.g.,neopentylglycol dimethacrylate, 1,6 hexanediol diacrylate, 1,3 butylenedimethacrylate, trimethylolpropane triacrylate, pentaerythritoltriacrylate, pentaerythritol tetraacrylate, etc.

Other vinyl containing compounds which are polymerizable with theabove-discussed organic resins upon introduction of ionizing radiation,are divinyl and tetravinyl compounds such as those disclosed by U.S.Pat. Nos. 3,586,527; 3,586,528; and 3,586,530. These compounds areformed by first reacting a diepoxide or monoepoxide with acrylic acidand/or methacrylic acid and then subsequently reacting the resultantester condensation product with a saturated acylhalide. The divinyl andtetravinyl compounds disclosed in these patents are homopolymerizableand copolymerizable with each other and with various monovinyl monomersmentioned above.

Still other compounds polymerizable with the alpha-beta olefinicallyunsaturated resins may be employed as the second binder component.Included in such compounds are the alpha-beta unsaturated siloxanestaught in U.S. Pat. Nos. 3,577,262 and 3,577,263 as well as thealpha-beta unsaturated diurethanes of U.S. Pat. No. 3,585,065 formed byreacting an unsaturated diisocyanate with an unsaturated polyester.

C. MONO- OR DIESTER OF PHOSPHORIC ACID

The coating compositions of the invention include between about 1.0 andabout 15.0 parts, preferably between about 3.0 and about 10.0 parts per100 parts of the total of said alpha-beta olefinically unsaturated resinand the compound polymerizable therewith of a triester of phosphoricacid bearing one or more sites of vinyl unsaturation and having theformula: ##STR4## where: R = H, Cl or CH₃

A = c_(n) H_(2n), 2 ≦ n ≦ 6

R' = c₁ to C₄ alkyl or C₁ to C₄ chloro- or bromoalkyl

Representative of the various species of organo-phosphate esters fallingwithin the above formula are: (1) tris (methacryloxyethyl) phosphate (R= CH₃ ; A = -C₂ H₄ -; m = 3); (2) tris (acryloyloxyethyl) phosphate (R =H; A = -C₂ H₄ -; m = 3); (3) dimethylmethacryloyloxyethyl phosphate (R =CH₃ ; A = -C₂ H₄ -; R' = CH₃ ; m = 1); (4) diethyl methacryloyloxyethylphosphate (R = CH₃ ; A = -C₂ H₅ -; m = 1); (5) dipropyl acryloyloxyethylphosphate (R = H; A = -C₂ H₄ -; R' = -C₃ H₇ -; m = 1); (6) methylbis(acryloyloxyethyl) phosphate (R = H, A = -C₂ H₄ -; m = 2; R' = CH₃); (7)ethylbis (acryloyloxyethyl) phosphate (R = H; A = -C₂ H₄ -; m = 2; R' =C₂ H₅ -); (8) methylbis (methacryloyloxyethyl) phosphate (R = CH₃ ; A =-C₂ H₄ -; m = 2; R' = CH₃); (9) ethylbis (methacryloyloxyethyl)phosphate (R = CH₃ ; H = -C₂ H₄ -; m = 2; R' = C₂ H₅ -); etc.

D. PHOTOINITIATORS

When the paint compositions of the invention are polymerized by exposureto ultraviolet radiation it may be desirable to include a photoinitiatoror photosensitizer in the paint. The use of such photoinitiators andexamples of various ones which may be employed will be discussedhereinafter in greater detail.

E. INERT SOLVENTS AND OTHER ADDITIVES

Inert solvents, i.e., solvents that do not enter into the polymerizationor crosslinking reactions of the paint binder polymer/monomer systemunder normal exposure to radiation, can be added to the coatingformulation to reduce viscosity and aid in control of applicationproperties. Such solvents are normally selected to be substantially morevolatile than the monomeric constituents of the paint formulation, thusallowing them to evaporate prior to irradiation of the coatings.Suitable solvents include, by way of example and not by way oflimitation: toluene:butyl acetate; methylethyl ketone; isopropanol;benzene; tetrahydrofuran; dioxane, methylisobutyl ketone; methylenechloride; chloroform; ethylene chloride; trichloroethylene;trichloroethane; and mixtures thereof. Additional materials such ascatalysts, pigments, plasticizers, etc., all of which are well known inthe formulation of coating compositions and, in particular in the art ofradiation polymerizable coating compositions, may be included in thecoating compositions of the invention.

II. COATED ARTICLES AND PROCESSES FOR MAKING SAME

The radiation polymerizable paints discussed above display unusuallygood adhesion to a variety of substrates including wood, paper, glass,shaped polymeric surfaces and metal, particularly vapor deposited metalsurfaces. In addition to these outstanding adhesion properties, thecoatings of the invention also exhibit excellent water resistance andintercoat adhesion. The novel paint compositions of the invention, likeprior art radiation polymerizable paints discussed above, may be appliedto a variety of substrates by conventional means, e.g., brushing,spraying, roller coating, flow coating, etc., to an average thicknesswhich is preferably in the range of from about 0.1 to about 4.0 milsdepending on the substrate and the intended end use of the coatedproduct.

The novel paint compositions of the invention may be cured orpolymerized by exposure to radiation, preferably ionizing radiation orultraviolet light. In either case, the paint compositions may be curedat relatively low temperatures, e.g., between room temperature (20° to25° C) and the temperature at which significant vaporization of its mostvolatile component is initiated, (ordinarily between about 20° C andabout 70° C).

The term "ionizing radiation" as employed herein means radiation havingsufficient energy to remove an electron from a gas atom, forming an ionpair, and hence radiation with energy of, or equivalent to, about 5,000electron volts. The preferred method of curing paint films of thisinvention by exposure to ionizing radiation is by subjecting such filmsto a beam of polymerization-effecting electrons which is at its sourceof emission within the range of, or equivalent to, 150,000 to 450,000electron volts. In this method of curing, it is preferred to employ aminimum of 25,000 electron volts per inch of distance between theradiation emitter and the workpiece where the intervening space isoccupied by air. Adjustment is made for the resistance of theintervening gas which is preferably an oxygen-free inert gas such asnitrogen, helium, or combustion products of natural gas. It is, however,within the scope of the use of ionizing radiation to effectpolymerization using either that which is conventionally termed "highenergy particle radiation" or "ionizing electromagnetic radiation".

When such ionizing radiation is employed to cure the paint compositionsof this invention, the radiation energy is applied at dose rates of fromabout 0.1 to about 100 Mrads per second upon a preferably movingworkpiece with the coating receiving a total dose in the range of fromabout 0.1 to about 100, preferably from about 1 to about 25 Mrads. Theabbreviation "Mrads" as employed herein means 1 million Rads. The term"Rads" means that dose of radiation which results in the absorption of100 ergs of energy per gram of absorber, e.g., coating film. Theelectron emitting means may be a linear electron accelerator capable ofproducing a direct current potentially in the range hereinbefore setforth. In such a device, electrons are ordinarily emitted from a hotfilament and accelerated through a uniform voltage gradient. Theelectron beam, which may be about 1/8 inch in diameter at this point isscanned in one direction to make a fan-shaped beam and then passedthrough a metal window, e.g., a magnesium-thorium alloy of about 0.003inch thickness.

As mentioned above, the radiation polymerizable coating compositions ofthis invention may also be cured by exposure to ultraviolet light.Preferably, paint compositions according to this invention which arecured by exposure to ultraviolet light contain little or no pigment.Upon exposure to light of wavelengths less than about 390 mμ , most ofthe vinyl monomers employed in the paint compositions of this inventionwill fragment and produce radicals which can initiate polymerization.However, in order to make more efficient use of the output of highintensity UV sources and thereby attain a commercially feasible rate ofcure, it is preferred to include a photoinitiator or photosensitizer incompositions to be cured by ultraviolet radiation.

Photoinitiators (or sensitizers) are substances, generally organiccompounds which, upon exposure to light of appropriate wavelength, giverise to or promote the production of polymerization initiating species.It is preferred to employ a photoinitiator which decomposes to yield, orotherwise results in the production of, one or more free radical speciesupon exposure to light having a wavelength of less than about 380 mμ .In order for any photochemical reaction to occur, there must be someoverlap between the wave length of light incident upon the reactionmedium (the coating) and the wave length absorbed by the photoinitiatingspecies. Thus, the selection of an appropriate photoinitiator dependsnot only upon its efficacy as a polymerization initiator, but also uponthe light source(s) used.

Many different types of free-radical initiators and sensitizers havebeen studied in acrylic systems and these are well known in the art. Therate of cure of the paint compositions of this invention, is, of course,a function of the type of initiator and its concentration, the intensityof incident light of appropriate wavelength and the type andconcentration of polymerization inhibitors. Also, the detailedcompositions of the coating formulation can have a significant effect onthe rate of cure, especially at low exposure levels. Thus, in the endanalysis, the amount of ultraviolet radiation which is necessary toachieve the desired properties in the final film formed from the paintcompositions of this invention will vary with the composition of thepaint itself and one of ordinary skill in this art will be able todetermine the optimal exposure to UV light in view of the variousfactors discussed above with a minimum of experimentation.

Included among the many suitable photoinitiators are: organic carbonylcompounds such as acetone, benzophenone, benzanthrone, benzoin, benzoinmethyl ether, 2,2-diethoxyacetophenone,2,2-dimethoxy-2-phenylacetophenone, benzoin n-butyl ether and benzoiniso-butyl ether; peroxides such as hydrogen peroxide, di-t-butylperoxide, ergosterol peroxide and benzoyl peroxide; organic sulphurcompounds such as diphenyl disulfides, dibenzoyl disulfides anddibenzothiazol disulfides; and azo compounds such as 2,2'azobis-(2-methylpropionitrile), α,α'-azobisisobutylronitrile,azomethane, azothane, α-azobis-1-cyclohexane carbonitrile; and otherwell known initiators such as 2-ethylhexyl-2-cyano-3,3-diphenylacrylate. Based on availability, solubility in the coatingcomposition of this invention, freedom from color and efficiency ofcuring at minimal UV exposure levels, the preferred photoinitiators are2,2-diethoxyacetophenone, benzophenone and 2-ethylhexyl-2-cyano-3,3-diphenylacrylate. The amount of each photoinitiator necessary tosuitably initiate polymerization in the paint compositions of thisinvention when curing by exposure to UV light will be apparent to thoseskilled in the art. It has been found, however, that generally thepresence of a photoinitiator in the amount of from about 0.5 to about5.0 parts per 100 parts of the total reactive vehicle solids in thepaint composition will produce adequate curing upon exposure to a lowpressure ultraviolet lamp.

A. COATED ARTICLES INCLUDING VAPOR DEPOSITED METALS

As discussed above, the coating compositions of this invention areparticularly suited as abrasion and corrosion resistant protectivecoatings for surfaces bearing vapor deposited metals. Such coatedarticles bearing vapor deposited metals are a particularly preferredembodiment of this invention since they are suitable for use as asubstitute for plated metal surfaces used for trim or brightwork on theexterior of automobiles.

Vapor deposition of metals, and in particular vacuum metallizing, is asimple and relatively low cost process by which thin layers of metalsare deposited on prepared surfaces of substrates such as metal, plastic,glass, paper and other materials. Surfaces bearing vapor depositedmetals, and in particular plastic substrates bearing thin deposits ofaluminum, have been considered as a substitute for plated metal surfacesused for trim or brightwork on the exterior of automobiles. Since vapordeposition of metals produces very attractive surfaces and issubstantially less expensive than processes for metal plating, such aschrome plating, it would appear to be ideally suited for producing suchtrim or brightwork. However, due to severe abrasion and corrosionproblems, articles produced by vapor depositing metals have not beendeemed suitable for exterior automotive use. The coating compositions ofthis invention, when applied over the surface of such vapor depositedmetals afford the protection necessary to overcome this problem.

Vapor deposition of metals is well known and the detailed procedureswill be apparent to those skilled in the art. Physical vapor deposition,the process most commonly used for decoration of plastics, involvesformation of the coating by physical means alone. Two of the mostcommonly used techniques, i.e., resistive heating and electron beamheating, involve stepwise heating in vacuum, first melting and thenvaporizing the material to be deposited. Other well known techniquessuch as sputtering may also be employed. The choice of methods dependsto some extent on the material to be deposited. A review of physicalvapor deposition techniques may be found in Vapor Deposition, C. F.Powell, J. H. Oxley and J. M. Blocker, Jr., eds., John Wiley & Sons,Inc. New York (1966), p. 221 ff. Resistive heating of a tungstenfilament or basket or of a refractory crucible is commonly used forvapor deposition of aluminum, the most common evaporant for depositionon plastic parts. Electron beam heating of an evaporant contained in asuitable crucible or hearth is recommended for deposition of alloys andmetals which have low vapor pressures or which form alloys withconventional filaments or crucibles at normal evaporating temperatures.Iron-chrome alloys can be deposited best using electron-beam heatingtechniques or sputtering.

Chemical vapor deposition techniques, also discussed in Powell et al,can in principle also be used in the formation of the composite coatedarticles of this invention. Such techniques involve the transfer ofmaterial across temperature or concentration gradients between thesubstrate and the surrounding atmosphere and formation of coatings bychemical reactions at the surface of the substrate. Chemical vapordeposition techniques often involve heating of the substrate tomoderately high temperatures to form the final metallic coating.Application of these techniques is thus restricted to those substratescapable of withstanding the required process conditions.

B. PREFERRED PLURAL COATED EMBODIMENT

The preferred coated article of this invention is prepared by: applyinga base coat to a substrate and curing the coating; vapor depositing ametal layer on the base coat; applying the coating composition of thisinvention over the metallized surface; and curing the coating withradiation.

C. BASE COAT COMPOSITIONS

The base coat fills minor surface imperfections of the substrate,provides a high-gloss surface to receive the metal deposit, improvesadhesion of the deposit, and reduces the quantity of gas liberated fromthe substrate at reduced pressures. In selecting a base coat it is thusimportant that the composition display good intercoat adhesion, i.e.,adhere well to both the substrate and the metal layer. Many base coatcompositions useful in metal vapor deposition processes are known in theart and one of ordinary skill in the art will, of course, select thecomposition best suited for the substrate and metal vapor being used.However, certain lacquers and radiation polymerizable base coats arepreferred for the preferred plural coated embodiment of this invention.

The lacquers and the radiation polymerizable compositions preferred asbase coats in the process of this invention may be applied byconventional means, e.g., spray coating, dip coating, flow coating,etc., to an average thickness which is preferably in the range of fromabout 0.1 to about 4.0 mils. The lacquers preferred as base coats arewell-known in the prior art and may be air dried or heat cured. Mostbake-curing lacquers cure in 1-3 hours at temperatures ranging from 140°to 180° F. The radiation polymerizable base coats may be cured atrelatively low temperatures, e.g., between room temperature (20° to 25°C) and the temperature at which significant vaporization of its mostvolatile reactive component is initiated, (ordinarily between about 20°C and about 70° C). The radiation energy is applied at dose rates offrom about 0.1 to about 100 Mrads per second upon a preferably movingworkpiece with the coating receiving a total dose in the range of fromabout 0.1 to about 100, preferably from about one to about 25 Mrads. Itwill be appreciated that the use of radiation polymerizable base coatswill substantially lessen the processing time necessary for producingthe plural coated articles of the invention.

The lacquer base coats which are preferred are well-known in the art ofvapor deposition, and in particular vacuum metallizing, and consistessentially of a thermoplastic or thermosetting resin in a volatilesolvent. Representative of the organic resins which may be employedindividually or in combination to formulate such a lacquer are: acrylicresins, alkyd resins (pure and modified), polyesters, conventionalvarnishes, urea-formaldehyde resins, vinyl polymers, acrylonitrilepolymers, phenolic resins, cellulosic resins, polyurethanes, butylrubber and chlorinated butyl rubber, silicone resins,melamine-formaldehyde resins, cellulosic resins, polyurethanes, butylrubber and chlorinated butyl rubber, silicone resins,melamine-formaldehyde resins, polyestyrenes, natural rubber, andmodified phenolic resins. Numerous base coats employing such organicresins are commercially available.

Radiation polymerizable base coat compositions which are preferred foruse in the process and articles of this invention include a coatingformulation including an alpha-beta olefinically unsaturated urethanemodified organic resin discussed above and disclosed in U.S. Pat. No.3,437,514. That composition, exclusive of non-polymerizable solvents,pigments and other non-reactive components consists essentially of: (1)between about 90 and about 10 parts, preferably between about 70 andabout 30 parts, of the alpha-beta olefinically unsaturated urethanemodified organic resin; and (2) between about 10 and about 90,preferably between about 30 and about 70 parts of vinyl solventmonomers. The alpha-beta olefinically unsaturated urethane modifiedorganic resin is formed by reacting a diisocyanate monomer and anorganic resin having in its molecular structure a plurality of hydrogenatoms which are labile with respect to the isocyanate group, e.g., alabile hydrogen of an amine, amide, alcohol or carboxylic acid, andsubsequently reacting the product with a hydroxylated vinyl monomer. Theorganic resin used in this preparation may be a polyester or a resinformed by copolymerization of acrylic monomers, i.e., acrylic andmethacrylic acids as well as esters formed therefrom. Exemplary of themany diisocyanates which may be employed to form the alpha-betaolefinically unsaturated resins are: 2,4 tolylene diisocyanate,65/35-Tolylene diisocyanate, 80/20 Tolylene diisocyanate,4,4'-diphenyl-methane diisocyanate, dianisidine diisocyanate, Tolidenediisocyanate, hexamethylene diisocyanate, etc.

The formulation of various polyesters, such as hydroxy terminatedpolyesters and polymers or copolymers formed from acrylic monomers andbearing functional groups which will react with the diisocyanatecompounds are well known in the art.

Another preferred formulation for use as a base coat in this inventionis disclosed in U.S. Patent Application Ser. No. 500,828 filed Aug. 26,1974 and entitled "Protective Coating Composition, Plural Coated Articleand Process for Preparing Same - A." That formulation, exclusive ofnon-polymerizable solvents, pigments and other non-reactive componentsconsists essentially of a solution of: (1) between about 90 and about 10parts, preferably between about 70 and about 30 parts, of a saturated,thermoplastic, vinyl polymer prepared from at least about 85 weightpercent of monofunctional vinyl monomers; and (2) between about 10 andabout 90 parts, preferably between about 30 and about 70 parts, of vinylsolvent monomers for said vinyl polymer, at least about 10 weightpercent of said solvent monomers being selected from the groupconsisting of divinyl monomers, trivinyl monomers, tetravinyl monomersand mixtures thereof.

The saturated, thermoplastic, vinyl resin polymers useful in the basecoat composition may be prepared from a single vinyl monomer or frommixtures of vinyl monomers by conventional polymerization techniques,e.g., suspension, emulsion, bulk or solution polymerization usingconventional free radical initiators such as peroxides andhydroperoxides as well as azobis (isobutyronitrile). Preferred monomersfor preparation of the vinyl homopolymer or copolymer resins aremonofunctional monoacrylates and monomethacrylates as well as monovinylhydrocarbons. The most preferred monomers are esters of acrylic ormethacrylic acid and C₁ C₈ monohydric alcohols, e.g., methylmethacrylate, butyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate,cyclohexyl acrylate and mixtures thereof. Monovinyl hydrocarbonssuitable in forming polymers are styrene and substituted styrenes, suchas alpha-methyl styrene, vinyl toluene, t-butyl styrene, chlorostyreneand mixtures thereof.

As indicated above, the saturated thermoplastic vinyl resin polymers orcopolymers useful in the base coat formulation of the invention shouldbe formed from at least 85 weight percent of monofunctional vinylmonomers. However, difunctional monovinyl monomers such as acrylic andmethacrylic acids, acrylamide, methacrylamide, 2-hydroxyethylmethacrylate, methacryloxyethyl phosphate and2-acrylamido-2-methylpropanesulfonic acid, may be used as a minorcomponent of the polymer, i.e., up to a combined total of about 15weight percent. The incorporation of such monomers may be desirable insome cases to provide a measure of polarity to the coating resin.However, it should be recognized that a concomitant effect of increasedpolarity is increased water sensitivity. Thus, it is preferred not toemploy such polar monomers in the preparation of the paints of thisinvention unless necessary for the particular application.

The essentially linear, gel-free thermoplastic polymers formed from thepreferred monomers set forth above should have number average molecularweights (M_(n)) of less than about 250,000 but not less than about2,000. Preferred values lie between about 3,000 and about 100,000 withmost preferred values being between about 5,000 and about 50,000.

While this base coat composition may include mixtures of polymers orcopolymers formed from vinyl monomers as discussed above, it ispreferred that the paint solution contain little or no alpha-betaolefinically unsaturated resins as conventionally employed inradiation-curable paint resins discussed above. Even though theproperties of the paint, particularly adhesion properties, will beaffected by its inclusion, up to 5 weight percent based on the totalpolymer and solvent monomer of such alpha-beta olefinically unsaturatedresins may be tolerated.

At least about 10 weight percent and preferably at least about 15 weightpercent of the vinyl solution monomers of this base coat formulation ofthe invention are selected from the group consisting of divinylmonomers, trivinyl monomers and tetravinyl monomers. These di-, tri-,and tetravinyl compounds are preferably acrylates, methacrylates orvinyl hydrocarbons. The most preferred are esters of acrylic ormethacrylic acids and polyhydric C₂ -C₈ alcohols, e.g., neopentylglycoldimethacrylate, 1,6-hexanediol diacrylate, 1,3-butylene dimethacrylate,trimethylolpropane triacrylate, pentaerythritol triacrylate, andpentaerythritol tetraacrylate. Other divinyl monomers which may beemployed are disclosed in U.S. Pat. Nos. 3,586,528; 3,586,529;3,586,530; 3,586,531; and 3,595,687. These divinyl compounds are formedby reacting either a monoepoxide or diepoxide with acrylic acid ormethacrylic acid and subsequently reacting the resultant estercondensation product with a saturated acyl halide or a vinyl unsaturatedacyl halide. Further tetravinyl compounds which may be employed aredisclosed in U.S. Pat. Nos. 3,586,526; 3,586,527; and 3,591,626. Thesetetravinyl compounds are formed by reacting a diepoxide with acrylicacid and/or methacrylic acid and then subsequently reacting theresultant ester condensation product with a vinyl unsaturatedacylhalide.

The remainder of the vinyl solvent monomers used to form this base coatin combination with the saturated, thermoplastic vinyl resin polymers orcopolymers discussed above may be monofunctional, monovinyl monomerssuch as those used in the preparation of the polymer or copolymer.

A further base coat formulation for use in the process and articles ofthis invention is disclosed in U.S. Pat. Application Ser. No. 537,736,filed Dec. 31, 1974 now U.S. Pat. 3,957,918 and entitled "ProtectiveCoating Composition, Plural Coated Article and Process for Making Same -D." The coating formulation disclosed in that application differs fromthat discussed in the first above-mentioned application by the inclusionin the composition of between about 1.0 and about 15.0 parts, preferablybetween about 3.0 and about 10.0 parts, per 100 parts of the total ofthe saturated, thermplastic resin and the vinyl monomer solvent of thesame triesters of phosphoric acid which are included in the compositionsof this application.

A final base coat composition which may be employed in making thepreferred plural coated articles of this invention is a compositionwhich is the same as that disclosed and claimed in the firstabove-mentioned application with the exception that the compositionincludes between about 0.05 and about 1.0 parts, preferably betweenabout 0.1 and about 0.6 parts, and still more preferably between about0.2 and about 0.5 parts, per 100 parts of the total of the saturatedthermoplastic polymer and the vinyl solvent monomer, of a mono- ordiester of phosphoric acid having the formula: ##STR5## where: R = H₁,Cl or CH₃

A = c_(n) H_(2n), 2 ≦ n ≦ 6

R' = h, c₁ to C₄ alkyl or C₁ to C₄ bromo- or chloroalkyl

It should be appreciated that it is within the scope of this inventionas defined above to employ various combinations of the various polymersin preparing the various coating compositions. Therefore, it should beunderstood that the following specific examples are presented by way ofillustration and not by way of limitation.

EXAMPLE I

a. A vinyl monomer comprising polymer is prepared from the followingreactants:

    ______________________________________                                                         Parts by Weight                                              ______________________________________                                        A. Methyl methacrylate                                                                           328                                                        B. Ethyl acrylate  549                                                        C. Glycidyl methacrylate                                                                         123                                                        D. Azobisisobutyronitrile                                                                        10                                                         E. Hydroquinone    0.4                                                        F. Tetraethyl ammonium bromide                                                                   3.6                                                        G. Methacrylic acid                                                                              74.5                                                       H. Xylene (solvent)                                                                              1000                                                       ______________________________________                                    

To a reaction vessel equipped with a stirrer, condenser, thermometer andnitrogen inlet and exit tubes is charged the xylene which is then heatedto a reflux temperature (138° C). To the refluxing xylene is added amixture of components A, B, C and D. Heating of the reaction mixture isthen continued at 135° C for 4 hours after which the reaction mixture iscooled to 90° C. After cooling, components E, G and F are added in thatorder and the temperature increased to 135° C. The reaction is thencontinued until an acid number of less than 1 is obtained after whichthe xylene solvent is removed by vacuum distillation.

b. A coating composition is prepared from the following components:

    ______________________________________                                                           Parts by Weight                                            ______________________________________                                        Unsaturated acrylic resin from (a)                                                                 55                                                       Neopentyl glycol diacrylate                                                                        10                                                       2-ethyl hexyl acrylate                                                                             14                                                       Tris (methacryloyloxyethyl) phosphate                                                              2.0                                                      ______________________________________                                    

c. The components of the composition are mixed together, reduced tospray viscosity (15 sec. Ford cup No. 4) with a 1:1 mixture of tolueneand butylacetate, sprayed on plastic substrates coated with vacuumdeposited aluminum and cured by electron beam irradiation at:

    ______________________________________                                        Average current density                                                                         275 Kilovolts                                               Current            30 Milliamps                                               Dose               7 Mrads                                                    Atmosphere        Nitrogen and carbon dioxide                                                   mixed (less than 1% oxygen)                                 ______________________________________                                    

The coating so obtained displays excellent adhesion, no softening orcolor change, and the underlying metal is similarly unaffected by 240hours exposure to water at 90° F. No failure is observed after 168 hoursin a 5% salt spray corrosion test booth (ASTM Test No. B-117).

EXAMPLE II

The procedure of Example I is repeated except that the tris(methacryloyloxyethyl) phosphate is omitted. The cured coatings exhibitvery poor adhesion (coatings fail taped cross-hatch adhesion tests) andallow removal of the underlying metal adjacent to a scribed line whenthe coated article is subjected to the salt spray exposures.

EXAMPLE III

The procedures of Example I are followed with the exception that 7.0parts of dimethyl methacryloyloxyethyl phosphate is used as the triesterand that the unsaturated acrylic resin is prepared in the followingmanner:

    ______________________________________                                        Step I Terpolymer  Parts by Weight                                            ______________________________________                                        (1) Methylmethacrylate                                                                           100                                                        (2) Butyl acrylate 60                                                         (3) Glycidyl methacrylate                                                                        40                                                         (4) t-Butyl Peroctoate                                                                           8                                                          (5) Xylene         300                                                        ______________________________________                                    

A mixture of items (1), (2), (3) and (4) is added dropwise over a 2-hourperiod to a reaction flask (equipped with a condenser, thermometer,agitator, and dropping funnel) containing (5) maintained at reflux witha nitrogen sparge throughout. The solution is maintained at reflux forat least 4 hours after addition is complete.

    ______________________________________                                        Step II Adduct     Parts by Weight                                            ______________________________________                                        (6) Hydroquinone   0.1                                                        (7) Acrylic acid   24.3                                                       (8) Tetraethyl amine                                                                             0.7                                                        ______________________________________                                    

(6) is added to the solution from Step I. The unsaturated acid (7) andcatalyst (8) are added to the refluxing solution. The esterificationreaction is continued at reflux until 90-95% of (7) is consumed. Thepolymer so obtained has a molecular weight (M_(n)) of 3,000.

The coating so obtained displays excellent adhesion to a variety ofsubstrates including metal, vapor deposited metals, wood, glass andpolymeric substrates. The coating displays excellent adhesion to vapordeposited stainless steel and does not soften or change color upon 240hours immersion in water at 90° F.

EXAMPLE IV

A coating composition is prepared in accordance with the procedures ofExample III with the exception that 3 parts per 100 parts of reactivesolids in the coating of 2,2 diethoxyacetophenone is added. This coatingcomposition is applied to a substrate comprising a surface of vapordeposited alloy of iron and chrome (80% Fe/20% Cr) and cured by exposureto UV light. The coating exhibits excellent abrasion and waterresistance.

EXAMPLE V

The procedure of Example IV is repeated with the difference that (1) anequimolar amount of styrene is substituted for methyl methacrylate inthe preparation of the vinyl monomer comprising polymer; and (2) 10.0parts ofmethylbis (acryloyloxyethyl) phosphate are employed. Thecoatings adhere well to metal substrates and provide adequate corrosionresistance.

EXAMPLE VI

A coating composition is prepared from the following components:

    ______________________________________                                                              Parts by Weight                                         ______________________________________                                        Unsaturated acrylic resin prepared in Example I                                                       55                                                    1,6 hexanedioldiacrylate                                                                              10                                                    2-ethylhexyl acrylate monomer                                                                         15                                                    diethylmethacryloyloxyethyl phosphate                                                                 6.0                                                   ______________________________________                                    

The above components are mixed, reduced to spray viscosity (15 sec FordCupN . 4) with a 1:1 mixture of toluene and butyl acetate sprayed onpanels ofvapor deposited aluminum and antimony and cured by electronbeam irradiation at:

    ______________________________________                                        Average current density                                                                         275 Kilovolts                                               Current            30 Milliamps                                               Dose               7 Mrads                                                    Atmosphere        Nitrogen and carbon dioxide                                                   (Less than 1% oxygen)                                       ______________________________________                                    

The films formed from the above composition display excellent adhesionand corrosion resistance when immersed in a 5% aqueous solution ofsodium chloride for a period of 30 days. The films also display nosoftening or color change, and the underlying metal is similarlyaffected by 240 hours exposure to water at 90° F.

EXAMPLE VII

A coating composition is prepared in accordance with Example VI exceptthat2 parts by weight of alpha 2,2 diethoxyacetophenone are included.

The film forming composition so obtained is applied to a substrate andcured thereon by exposure for 3 minutes in a nitrogen atmosphere toradiation from a low pressure mercury lamp (intensity about 4 × 10¹⁶photons sec. ⁻ ¹ cm. ⁻ ², major UV peak at 2537 angstroms) at a distanceof 1 inch. The cured coating displays adhesion to metal and vapordeposited aluminum and solvent and water resistance essentiallyequivalent to those of a comparable electron beam curing coating.

EXAMPLE VIII

To 75 parts by weight of a paint binder solution comprising analpha-beta olefinically unsaturated polyester resin prepared inaccordance with Example I of U.S. Pat. No. 3,437,514 is added 1.25 partsof tris(acryloyloxyethyl) phosphate. The binder solution is mixed,applied toa vacuum metallized substrate and cured by electron beamirradiation. The resultant coatings adhere well and provide adequateprotection in a 5% salt spray.

EXAMPLE IX

To 75 parts by weight of the silicone-modified polyester paint binderresinprepared in accordance with Example XV of U.S. Pat. No. 3,437,514is added 5.0 parts by weight of dipropylacryloyloxyethyl phosphate and1.3 parts byweight of 2-ethylhexyl 1-2 cyano 3,3-diphenylacrylate. Theresin binder solution is mixed, applied to a plastic substrate bearing avapor deposited metal layer and cured by exposure to UV irradiation. Thecoatings adhere well and provide adequate protection upon waterimmersion and exposure to a 5% salt spray.

EXAMPLE X

To 90 parts by weight of each of the paint dispersions prepared inaccordance with Example I of U.S. Pat. No. 3,660,145 is added 11.5 partsby weight of ethylbis(acryloyloxyethyl) phosphate. The dispersions areapplied to metal substrates by spraying and cured by electron beamirradiation. The coatings adhere well and provide adequate protectionuponwater immersion and exposure to 5% salt spray.

EXAMPLE XI

a. An alpha-beta olefinically unsaturated urethane modified organicresin is prepared from the following components:

    ______________________________________                                                         Mole Percent                                                                           Wt. Percent                                         ______________________________________                                        (1) Adipic acid    24         28.0                                            (2) Maleic anhydride                                                                             8          5.6                                             (3) Neopentylglycol                                                                              38         31.1                                            (4) Hexamethylenediisocyanate                                                                    16         22.1                                            (5) 2-hydroxyethyl acrylate                                                                      14         13.2                                            ______________________________________                                    

Components (1), (2) and (3) are charged to a reaction vessel equipped inthe usual way for a polyester synthesis (i.e., so that water can beremoved during the course of the reaction) and heated gradually to 230°C. When an acid value less than 16 is obtained (average reaction time4.5 hours), the mixture is cooled to 150° C and 0.04 weight percenthydroquinone is added. The mixture is further cooled to below 100° C andreduced to 70% solids with butyl acrylate.

Component (4) is added at room temperature and the mixture is heated at60-70° C until an isocyanate level of 5% is obtained.

Component (5) is added at 70° C and the mixture is heated at 80-100° Cuntil the isocyanate is essentially completely reacted. The mixture isreduced to 60% solids with equal parts 2-hydroxyethyl acrylate and butylacrylate.

b. A coating composition is prepared from the following components:

    ______________________________________                                                               Parts by Weight                                        ______________________________________                                        (1) Resin solution from (a)                                                                            65                                                   (2) 2-ethylhexyl acrylate                                                                              25                                                   (3) Neopentylglycol diacrylate                                                                         10                                                   (4) Methylbis(methacryloyloxyethyl) phosphate                                                          3.5                                                  ______________________________________                                    

c. The above components are mixed, applied to plastic substrates bearingvapor deposited aluminum and cured by electron beam irradiation in anitrogen atmosphere at:

    ______________________________________                                        Average current density                                                                         295 Kilovolts                                               Current            20 Milliamps                                               Total Dose         10 Mrads                                                   ______________________________________                                    

The resultant films are abrasion resistant and the metallized surfacedoes not corrode after immersion of a scribed panel in water at 90° Fand immersion in a 5% salt spray.

EXAMPLE XII

A plural coated article including a vacuum deposited metal layer isprepared as follows:

A. Preparation and Application of Base Coat

    ______________________________________                                        Step I Preparation of Polymeric Intermediate                                                   Mole Percent                                                                           Wt. Percent                                         ______________________________________                                        (1) Adipic Acid    24         28                                              (2) Maleic Anhydride                                                                             8          5.6                                             (3) Neopentyl glycol                                                                             38         31.1                                            (4) Hexanethylenediisocyanate                                                                    16         22.1                                            (5) 2-hydroxyethylacrylate                                                                       14         13.2                                            ______________________________________                                    

Components (1), (2) and (3) are charged to a reaction vessel equipped inthe usual manner for polyester synthesis (i.e., so that water can beremoved during the course of the reaction) and heated gradually to 230°C. When an acid value of less than 16 is obtained (average reaction time16 hours), the mixture is cooled to 150° C and 0.04 weight percenthydroquinone is added. The mixture is further cooled to below 100° C andreduced to 70% solids with butyl acrylate.

Component (4) is added at room temperature and the mixture heated at60-70° C until an isocyanate level of 5% is obtained.

Component (5) is added at 70° C and the mixture heated at 80°-100° Cuntil the isocyanate is completely reacted. The mixture is reduced to60% solids with equal parts of 2-hydroxyethylacrylate and butylacrylate.

    ______________________________________                                        Step II Preparation of the Coating Formulation                                                 Parts by Weight                                              ______________________________________                                        (1) Resin Solution from I                                                                        60                                                         (2) 2-ethylhexylacrylate                                                                         10                                                         (3) hydroxyethylacrylate                                                                         20                                                         (4) methylmethacrylate                                                                           40                                                         ______________________________________                                    

The listed components are mixed in indicated proportions by weight,sprayedon a plastic substrate and cured with an electron beam in anitrogen atmosphere at 280 KV, 40 ma, total dose of 10 Mrads.

B. A layer of 430 stainless steel is deposited on the base coat byconventional vapor deposition technique employing electron beam heatingofthe evaporant.

C. Preparation and Application of Top Coat

    ______________________________________                                        Step I Preparation of Alpha-Beta Olefinically Unsaturated                     ______________________________________                                        Resin                                                                                           Parts by Weight                                             ______________________________________                                        (1) Methyl methacrylate                                                                           328                                                       (2) Ethylacrylate   549                                                       (3) Glycidyl methacrylate                                                                         123                                                       (4) Azobisisobutyronitrile                                                                        10                                                        (5) Hydroquinone    0.4                                                       (6) Tetraethyl ammonium bromide                                                                   3.6                                                       (7) Methacrylic acid                                                                              74.5                                                      (8) Xylene (solvent)                                                                              1000                                                      ______________________________________                                    

To a reaction vessel equipped with a stirrer, condenser, thermometer andnitrogen inlet and exit tubes is charged the xylene which is then heatedto a reflux temperature (138° C). To the refluxing xylene is added amixture of components (1), (2), (3) and (4). Heating of the reactionmixture is then continued at 135° C for 4 hours after which the reactionmixture is cooled to 90° C. After cooling, components (5),(6) and (7)are added in that order and the temperature increased to 135° C. Thereaction is then continued until an acid number of lessthan 1 isobtained after which the xylene solvent is removed by vacuumdistillation.

    ______________________________________                                        Step II Preparation of the Top Coat Formulation                                                    Parts by Weight                                          ______________________________________                                        Unsaturated Acrylic Resin from I                                                                     55                                                     Neopentylglycoldiacrylate                                                                            10                                                     2-ethylhexyl acrylate  14                                                     ethylbis(methacryloyloxyethyl) phosphate                                                             14                                                     ______________________________________                                    

The above components of the formulation are mixed together, reduced tospray viscosity (15 sec., Ford cup No. 4) with a 1:1 mixture of tolueneand butyl acetate, sprayed on the vapor deposited metal surface andcured by electron beam irradiation (average current density -- 275KV;current --30ma; Dose --7 Mrads; atmosphere -- Nitrogen and carbondioxide mixed less than 1% oxygen).

The resultant metallized article passes cross-hatch adhesion tests, canwithstand a minimum of 50 rubs with a cloth soaked in methylethylketone. Also, the plural coated article is unaffected by immersion inwater at 90° F for 240 hours and 10 day immersion in a 5% aqueous sodiumchloride solution.

EXAMPLE XIII

The procedure of Example XII is repeated with the exception that: (1)The top coat formulation is prepared by adding 12.5 parts oftris(methylacryloyloxyethyl) phosphate to 75 parts by weight of a paintbinder solution comprising an alpha-beta olefinically unsaturatedpolyester resin prepared in accordance with Example I of U.S. Pat. No.3,437,514; and (2) The top coat formulation is applied to the metallizedsurface by flow coating. The resultant plural coated article exhibitsexcellent adhesion properties and is not affected by 240 hours exposuretoeither water at 90° F or a 5% aqueous sodium chloride solution.

EXAMPLE XIV

The procedure of Example XII is repeated with the exception that theunsaturated acrylic resin is prepared in the following manner:

    ______________________________________                                        Step I Preparation of the Terpolymer                                                           Parts by Weight                                              ______________________________________                                        (1) Methylmethacrylate                                                                           100                                                        (2) Butylacrylate  60                                                         (3) Glycidyl methacrylate                                                                        40                                                         (4) T-butyl peroctoate                                                                           8                                                          (5) Xylene         300                                                        ______________________________________                                    

A mixture of items (1), (2), (3) and (4) is added dropwise over atwo-hour period to a reaction flask equipped with condenser,thermometer, agitator and dropping funnel and containing (5) maintainedat reflux for at least 4hours after the addition is complete.

    ______________________________________                                        Step II - Preparation of the Adduct                                                          Parts by Weight                                                ______________________________________                                        (6) Hydroquinone 0.1                                                          (7) Methacrylic acid                                                                           24.3                                                         (8) Tetraethylamine                                                                            0.7                                                          ______________________________________                                    

(6) is added to the solution from Step I. The unsaturated acid (7) andcatalyst (8) are added to the refluxing solution. The esterificationreaction is continued at reflux until 90-95% of (7) is consumed. Thepolymer so obtained has a molecular weight (M_(n)) of 3,000.

The plural coated article passes cross-hatch adhesion tests, withstandsat least 50 rubs with a cloth soaked in methylethyl ketone and shows nodeleterious effects from exposure to water at 90° F and an aqueous 5%salt solution for 240 hours.

EXAMPLE XV

The procedure of Example XII is repeated with two exceptions: (1) thebase coat composition is prepared from commercial electron beampolymerizable resins as follows:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        (1) RD 2107-30*   40                                                          (2) RD 2278-58*   20                                                          (3) Hydroxyethylacrylate                                                                        50                                                          (4) Methylmethacrylate                                                                          10                                                          ______________________________________                                        *Both of these resins are unsaturated polyurethanes manufactured by Hughso    Chemical Company of Erie, Pennsylvania. (1) is supplied as a solution of       80% polymer, 20% 2-ethylhexylacrylate, (2) is supplied as a solution of       70% polymer, 15% methyl methacrylate, and 15% 2-ethyl-hexylacrylate; and      (2) 4.0 parts of dimethyl acryloyloxyethyl phosphate are employed as the      organophosphate ester component.                                         

(1) is supplied as a solution of 80% polymer, 20% 2-ethylhexylacrylate,(2)is supplied as a solution of 70% polymer, 15% methyl methacrylate,and 15% 2-ethylhexylacrylate; and (2) 4.0 parts of dimethylacryloyloxyethyl phosphate are employed as the organophosphate estercomponent.

The coated article so obtained passes cross-hatch adhesion tests and canwithstand a minimum of 50 rubs with a cloth soaked in methylethylketone. The surface coating does not soften or change colors and theunderlying metal is similarly unaffected by 240 hours exposure to waterat 90°F. No failure is observed in 240 hours immersion in a 5% aqueoussodium chloride solution.

EXAMPLE XVI

The procedure of Example XII is repeated with the exception that: (1) anequimolar amount of styrene is substituted for methylmethacrylate in thepreparation of the vinyl monomer comprising polymer; and (2) 7.0 partsof ethylbis (acryloyloxyethyl) phosphate are employed. The plural coatedarticle is of comparable quality with that of Example XII.

EXAMPLE XVII

The procedure of Example XII is repeated with the exception that thebase coat comprises a commercially available base coat lacquer Red SpotSM 1817sold by Red Spot Paint and Varnish Company and including aurealkyd type polymer. The base coat is applied to the substrate andcured by heating for 90 minutes at 170° F. The plural coated articlewithstands a minimum of 50 rubs with a cloth soaked in methyl ethylketone, passes cross-hatch adhesion tests and exhibits no deleteriouseffects from exposure for 240 hours to either water at 90° F or a 5%aqueous solution of sodium chloride.

EXAMPLE XVIII

A plural coated article is prepared as follows:

A. The same base coat as applied in Example XVII is applied to a plasticsubstrate by dip coating and cured by heating to 170° F for 90 minutes.

B. An iron/chrome alloy layer (80% Fe/20% Cr) is applied by conventionalvapor deposition techniques.

C. A top coat having the following formulation is prepared:

    ______________________________________                                                              Parts by Weight                                         ______________________________________                                        (1) Unsaturated acrylic resin prepared in                                      Example XII.           55                                                    (2) 2-ethylhexyl acrylate monomer                                                                     15                                                    (3) 1,6 hexanedioldiacrylate                                                                          10                                                    (4) diethyl methylacryloyloxyethyl phosphate                                                          8                                                     ______________________________________                                    

The above components are mixed, reduced to spray viscosity (15 sec. FordCup No. 4) with a 1:1 mixture of toluene and butylacetate, sprayed onthe vapor deposited surface and cured by exposure to electron beamirradiationat:

    ______________________________________                                        Average Current Density                                                                          275 KV                                                     Current             30 ma                                                     Dose                7 Mrads                                                   Atmosphere         Nitrogen and carbon                                                           dioxide (less than 1%                                                         oxygen)                                                    ______________________________________                                    

The resultant plural coated article passes cross-hatch adhesion tests,withstands a minimum of 60 rubs with a cloth soaked in methylethylketone and is not affected by exposure for 240 hours to either water at90° F or a 5% aqueous solution of sodium chloride.

EXAMPLE XIX

A plural coated article is prepared as follows:

A. A lacquer base coat, Red Spot SM 1817 is flow coated onto a plasticsubstrate and cured;

B. An aluminum layer is applied to the base coat surface by conventionalvacuum deposition technique.

C. A top coat having the same composition as employed in Example XIVexceptfor the use of 7.0 parts of diethylacryloyloxyethyl phosphate asthe organosphosphate additive is sprayed onto the metallized surface andcuredby exposure to an electron beam (9 Mrad dose).

The resultant plural coated article exhibits good adhesion as well asexcellent solvent resistance and corrosion resistance.

EXAMPLE XX

The procedure of Example XIX is repeated with the exception that the topcoat is prepared by adding 6.0 parts of diethylacryloyloxyethylphosphate to 75 parts by weight of the silicone-modified polyestersolution preparedin accordance with Example XV of U.S. Pat. No.3,437,514. The resultant plural coated article is of comparable qualitywith the article of ExampleXIX.

EXAMPLE XXI

A plural coated article is prepared as follows:

A. Preparation and application of Base Coat Formulation.

An electron beam polymerizable coating is prepared from the followingmaterials in the manner hereinafter set forth:

    ______________________________________                                        Step I Preparation of resin                                                                   Parts by Weight                                               ______________________________________                                        (1) Water         150                                                         (2) Triton X200*  5.2                                                         (3) 1% aqueous K.sub.2 S.sub.2 O.sub.8                                                          30                                                          (4) Methyl methacrylate                                                                         300                                                         (5) Water         270                                                         (6) Triton X200*  3.5                                                         (7) Triton X305*  10.7                                                        (8) K.sub.2 S.sub.2 O.sub.8                                                                     1.2                                                         (9) Octanethiol   2.1                                                         ______________________________________                                          *Triton X200, a product of Rohm & Haas Co., is an anionic surfactant         containing 28% active component (the sodium salt of an alkyl aryl             polyester sulfonate).                                                        **Triton X305, a product of Rohm & Haas Co., is a nonionic surfactant          containing 70% active component (an alkyarylpolyether alcohol averaging 3    ethylene oxide units).                                                    

Items 1 and 2 are charged to a reactor provided with a condenser, athermometer, an agitator, and a dropping funnel. The mixture is boiledto remove dissolved oxygen, and cooled slightly to 90° C. Item 3 isadded. A mixture of the remaining ingredients is then added slowly overa period of about 40 minutes while maintaining the reaction mixture atreflux. Following the monomer addition, the mixture is maintained atreflux for an additional 2 hours.

The latex so obtained is cooled and coagulated by adding it dropwise tothree volumes of rapidly stirred methanol heated to about 40° C. Thepolymeric precipitant is isolated by filtration, washed withmethanol,dried in vacuo and used in the subsequent preparation ofcoating materials.The polymer molecular weight (M_(n)) is about 10,000.

    ______________________________________                                        Step II Formulation of Coating                                                                   Parts by Weight                                            ______________________________________                                        (1) Polymer from Step I                                                                          24.2                                                       (2) Neopentylglycol diacrylate                                                                   36.4                                                       (3) 2-ethylhexyl acrylate                                                                        39.4                                                       (4) Butyl acetate  40                                                         (5) Toluene        40                                                         (6) Methyl ethyl ketone                                                                          10                                                         (7) Isopropanol    10                                                         ______________________________________                                    

A solution of polymer is prepared using the above-listed monomers andsolvents. The film-forming solution so obtained is applied to a plasticsubstrate and is cured thereon under an inert atmosphere by electronbeam irradiation using a total dosage of 9 Mrads (voltage 275 kv.,current 40 ma).

B. An aluminum layer is applied to the base coat by conventional vapordeposition technique.

C. The same top coat as employed in Example XII is applied to themetallized surface by flow coating.

The resultant plural coated article displays excellent adhesionproperties and withstands at least 50 rubs with a cloth soaked in methylethyl ketone. The article also is not adversely affected by exposure for240 hours to either water at 90° F or a 5% aqueous sodium chloridesolution.

EXAMPLE XXII

A plural coated article is prepared as follows:

A. A base coat having the following formulation is applied to an ABS(acrylonitrile-butadiene-styrene copolymer) plastic substrate and curedbyelectron beam irradiation:

    ______________________________________                                                          Parts by Weight                                             ______________________________________                                        (1) Acryloid B82     50                                                       (2) Pentaerythritol triacrylate                                                                   100                                                       ______________________________________                                    

The solution is adjusted to spray viscosity by dilution with a mixtureof butyl acetate, toluene, methyl ethyl ketone and isopropanol inproportion by weight 4:1:1:1.

B. A layer of type 430 stainless steel is applied to the surface of thebase coat by conventional vacuum deposition technique employing electronbeam heating of the evaporant.

C. A top coat having the same formulation as in Example XIV is appliedto the metallized surface by spraying and cured by exposure to electronbeam irradiation.

The resultant plural coated article passes cross-hatch adhesion testsand withstands a minimum of 50 rubs with a cloth soaked in methylethylketone.The article is also not adversely affected by exposure for aperiod of 240 hours to water at 90° F or a 5% aqueous sodium choridesolution.

EXAMPLE XXIII

A plural coated article is prepared as follows:

A. Preparation and application of Base Coat

The base coast composition is formulated from the following materials:

    ______________________________________                                                           Parts by Weight                                            ______________________________________                                        (1) Acryloid B48N* (solids basis)                                                                  35                                                       (2) 2-ethylhexylacrylate                                                                           30                                                       (3) Neopentylglycol diacrylate                                                                     35                                                       ______________________________________                                        *Acryloid B48N is marketed by Rohm & Haas Co. and is described as a methyl     methacrylate copolymer having a glass transition temperature of 50.degree    C. It is supplied as a 45% by weight solution in toluene at Brookfield         viscosity of 6,000 to 10,000 at 25° C. The number average molecula    weight is about 15,000. The composition is reduced to spray viscosity usin    an inert solvent mixture of toluene, methyl ethyl ketone, butyl acetate,       and isopropanol in a ratio of 4:4:1:1, sprayed on a metal substrate and       cured by electron beam irradiation.                                      

B. An aluminum layer is applied to the base coat surface by conventionalvacuum deposition technique.

C. Top coat formulations are prepared by adding 6.0 parts by weight ofethylbis (acryloyloxyethyl) phosphate to the coating dispersions formedinaccordance with Example I of U.S. Pat. No. 3,660,145. The pluralcoated articles formed by applying each of the top coats so formed tothe metallized surface and curing by electron beam irradiation allexhibit good adhesion properties and withstand a minimum of 50 rubs witha cloth soaked in methyl ethyl ketone. The articles also withstandexposure for 240 hours to both water at 90° F and a 5% sodium chloridesolution.

EXAMPLE XXIV

A plural coated article is prepared as follows:

A. A base coat having the following formulation is prepared:

    ______________________________________                                                           Parts by Weight                                            ______________________________________                                        (1) Elvacite 6011* (40% solids in a                                            30/70 mixture of acetone and toluene)                                                             40.0                                                     (2) Trimethylolpropane triacrylate                                                                 24.0                                                     (3) Hydroxypropylacrylate                                                                          8.0                                                      (4) 2-ethylhexylacrylate                                                                           16.0                                                     (5) Methyl ethyl ketone                                                                            12.0                                                     ______________________________________                                        *Elvacite 60111 is a methyl methacrylate polymer manufactured by DuPont.       The inherent viscosity of a solution of .25 grams polymer is 50 ml            chloroform measured at 25° C in a No. 50 Cannon-Fenske viscometer      is .34.                                                                  

The above materials are mixed together and the formulation reduced tosprayviscosity (No. 1 Zahn Cup, 40 secs) with a 1:1 mixture of tolueneand butylacetate. The formulation is then sprayed onto a plasticsubstrate and curedby electron beam irradiation.

B. An antimony layer is applied to the base coat surface by conventionalvacuum deposition technique.

C. A top coat formulation is prepared as follows:

a. An alpha-beta olefinically unsaturated urethane modified organicresin is prepared from the following components:

    ______________________________________                                                         Mole Percent                                                                           Wt. Percent                                         ______________________________________                                        (1) Adipic Acid    24         28.0                                            (2) Maleic anhydride                                                                             8          5.6                                             (3) Neopenthylglycol                                                                             38         31.1                                            (4) Hexamethylenediisocyanate                                                                    16         22.1                                            (5) 2-hydroxyethyl acrylate                                                                      14         13.2                                            ______________________________________                                    

Components (1), (2) and (3) are charged to a reaction vessel equipped inthe usual way for a polyester synthesis (i.e., so that water can beremoved during the course of the reaction) and heated gradually to 230°C. When an acid value less than 16 is obtained (average reaction time4.5 hours), the mixture is cooled to 150° C and 0.04 weight percenthydroquinone is added. The mixture is further cooled to below 100° C andreduced to 70% solids with butyl acrylate.

Component (4) is added at room temperature and the mixture is heated at60°-70° C until an isocyanate level of 5% is obtained.

Component (5) is added at 70° C and the mixture is heated at 80°-100° Cunti the isocyanate is essentially completely reacted. The mixture isreduced to 60% solids with equal parts 2-hydroxyethyl acrylate and butylacrylate.

b. A coating composition is prepared from the following components:

    ______________________________________                                                             Parts by Weight                                          ______________________________________                                        (1) Resin solution from (a)                                                                          65                                                     (2) 2-ethylhexyl acrylate                                                                            25                                                     (3) Neopentylglycol diacrylate                                                                       10                                                     (4) Dimethyl acryloyloxyethyl phosphate                                                              3.5                                                    ______________________________________                                    

The above materials are mixed, reduced to spray viscosity and sprayed onthe metallized surface. The resultant plural coated article passescross-hatch adhesion tests and exhibits good solvent resistance andcorrosion resistance.

EXAMPLE XXV

The procedure of Example XXI is repeated with the exception that 5.0parts of diethyl methacryloyloxyethyl phosphate are included in the basecoat formulation. The plural coated article is comparable to that ofExample XXI.

EXAMPLE XXVI

The procedure of Example XXII is repeated with the exception that 7.5partsof ethylbis (acryloyloxyethyl) phosphate are included in the basecoat formulation. The plural coated article is comparable to that ofExample XXII.

EXAMPLE XXVII

The procedure of Example XXII is repeated with the exception that 0.25parts of methyl (2-methacryloyloxyethyl) phosphate are included in thebase coat formulation. The plural coated article is comparable to thearticle of Example XXII.

EXAMPLE XXVIII

The procedure of Example XXIII is repeated with the exception that 0.4parts of ethylmethacryloyloxyethyl phosphate are included in the basecoatformulation. The plural coated article is of comparable quality tothat of Example XXIII.

It will be understood by those skilled in the art that modifications canbemade in the foregoing examples and within the scope of the inventionas hereinbefore described and hereafter claimed.

We claim:
 1. In a coating composition polymerizable by ionizingradiation which, exclusive of non-polymerizable solvents, pigments,initiators and other nonreactive components, consists essentially of asolution of: (1) an alpha-beta olefinically unsaturated organic resincontaining between about 0.5 and about 5 units of unsaturation per 1000units of molecular weight; and (2) a vinyl compound polymerizable withsaid resin upon exposure to radiation, the improvement comprisingincluding in said paint from about 1.0 to about 15.0 parts per 100 partsof the total of said organic resin and said compound polymerizable withsaid resin of a triester of phosphoric acid which bears one or moresites of vinyl unsaturation and has the formula: ##EQU1## where: R=H, Clor CH₃ A=c_(n) H_(2n), 2 ≦ n ≦ 6 R' = c₁ to C₄ alkyl or C₁ to C₄ chloro-or bromo-alkyl.
 2. A coating composition in accordance with claim 1wherein said organophosphate ester is selected from the group consistingof: (1) tri(methacryloyloxyethyl) phosphate; (2) tris(acryloyloxyethyl)phosphate; (3) dimethyl methacryloyloxyethyl)phosphate; (4)diethylmethacryloyloxyethyl)phosphate; (5)dipropylacryloyloxyethyl)phosphate; (6) methylbis(acryloyloxyethyl)phosphate; (7) ethylbis (acryloyloxyethyl)phosphate;(8) methylbis (methacryloyloxyethyl)phosphate; and (9) ethylbis(methacryloyloxyethyl)phosphate.
 3. A coating composition in accordancewith claim 1 wherein said triester of phosphoric acid is included in anamount ranging from about 3.0 to about 10.0 parts by weight per 100parts of the total of said organic resin and said compound polymerizablewith said resin.
 4. A coating composition in accordance with claim 1wherein said compound polymerizable with said resin comprises a solutionof vinyl monomers.